1. Field of the Invention
The present invention relates to a feeding mechanism for feeding filler wire to a welding torch or gun, and more particularly to an improved device for adjusting an engagement pressure within the feeding mechanism.
2. Description of the Related Art
Materials can be joined together by welding or brazing them together with a filler material, such as, for example, steel or aluminum wire (i.e., xe2x80x9cfiller wirexe2x80x9d). This typically involves the use of a welding machine (e.g., an arc welding gun or torch) to melt the filler wire at the junction of the two materials that are to be joined. To produce a strong and reliable weld, it is important that the filler wire be supplied smoothly and continuously to the welding gun. Typically, the filler wire is provided to the welding gun through a conduit, which is connected to a remote wire-feeding unit. Within the wire-feeding unit, the filler material is typically coiled about a reel, which is rotatably mounted within the unit.
There are several systems for delivering the filler wire in the wire-feeding unit to the welding gun. For example, in a pull-type feed system, the welding gun includes a feeding mechanism that pulls the wire from the wire-feeding unit. In a push-type feed system, the wire-feeding unit includes a feeding mechanism, which pulls the wire from the reel and then pushes the wire through the conduit towards welding gun. A push-pull type feed system utilizes a feeding mechanism in both the welding gun and the wire-feeding unit.
The push-pull type feed systems are generally preferred because of their superior performance. As mentioned above, these system typically include a feeding mechanism in both the welding gun and the wire-feeding unit. These feeding mechanisms typically include a motor, an idler roll and a drive roll, which is driven by the motor. The filler wire passes through the space between the driver roll and the idler roll. Preferably, the idler roll is provided with an adjustment mechanism for adjusting the engagement pressure between the idler roll and the drive roll.
The motor in the wire-feed cabinet is typically referred to as a xe2x80x9cslave motorxe2x80x9d, while the motor in the welding torch is typically referred to as a xe2x80x9cgun motorxe2x80x9d. Typically, the slave motor is a torque motor or a torque-type motor, which runs at a higher speed, but lower torque than the gun motor. The gun motor is typically a DC motor, which runs at a lower speed than the slave motor, but operates at a higher torque. As such, the feeding mechanism in the wire-feed cabinet is always trying to provide filler wire at a faster rate than the feeding mechanism in the welding gun. However, because the wire feeding mechanism in the welding gun is controlling the rate of wire feed, the column strength of the filler wire in the conduit controls the slave motor. Thus, the two wire feeding mechanisms operate at the same speed, which reduces the tendency of the filler wire to bind and/or compress within the conduit.
In order for the push-pull system to work properly, it is important that the engagement pressure between the idler roll and the driver roll in the wire-feed unit be adjusted properly. As mentioned above, the idler roll can be provided with an adjustment mechanism for adjusting the engagement pressure. An example of such an adjustment mechanism can be found in U.S. Pat. No. 6,064,036. The disclosed idler roll is secured to a pivot arm. A bolt and spring hold the arm in place during the welding process and bias the idler roll against the drive roll. The engagement pressure can be adjusted by tightening the bolt and changing the distance between the bolt and the pivot arm. In this manner, the engagement pressure can be adjusted by compressing or decompressing the spring.
This method of adjusting the engagement pressure has several disadvantages. For example, to find the proper position of the bolt, the operator typically routes the filler wire between the driver roll and the idler roll in the wire-feed unit. The operator then must prevent the wire spool from turning with the palm of one hand while at the same time grasping the bolt. With his other hand, the operator must actuate a trigger on the welding gun to operate the feed mechanism. The operator slowly tightens the bolt and increases the engagement pressure until the slave motor stalls. At this condition, the engagement pressure is proper and the wire does not slip even if a small amount of pressure is added to the wire as it exists the welding gun. If the engagement pressure is too small, the drive roll slips on the filler wire. If the engagement pressure is to large, the idler roll can cut into the wire causing excessive wire residue buildup. Too much engagement pressure also tends to flatten and deform the shape of the wire.
The method described above for adjusting the engagement pressure is time consuming, involves a relatively high level of dexterity and is subject to human error. Moreover, when the type of filler wire or wire sized is changed (e.g., from aluminum to steel), the engagement pressure must be readjusted. The engagement pressure must be readjusted because steel wires typically result in a higher column strength, as compared to aluminum wires) in the conduit. Moreover, steel wires tend to be harder than aluminum wires. As such, the engagement force should be larger for steel wires as compared to aluminum wires.
Accordingly, one aspect of the present invention involves a welding filler wire feed apparatus for feeding filler wire to a welding gun. The apparatus comprises a main frame and a secondary frame configured to move relative to said main frame. A first wheel is supported by the main frame and defines a first surface for contacting a first side of a filler wire. A second wheel is supported by the second frame and defines a second surface for contacting a second side of the filler wire. The second surface generally opposes the first surface. A motor is connected to at least one of the first wheel and the second wheel so as to selectably drive the at least one of said first wheel and said second wheel. A bias controller that includes a first resilient portion that biases the secondary frame such that the second surface is biased towards the first surface. The bias controller having a first preset position and a second preset position. In the first preset position, the first resilient portion exerts a first force on the secondary frame and in the second preset position, the first resilient portion exerts a second force on said secondary frame. The first force is greater than said second force.
Another aspect of the of the present invention involves a welding filler wire feed apparatus for feeding filler wire to a welding gun. The apparatus comprises a source of filler wire, a drive wheel, a motor, and a idler wheel. The drive wheel defines a first surface for contacting a first side of the filler wire. The motor is connected to the drive wheel so as to selectably drive the drive wheel. The idler wheel defines a second surface that is generally opposed to the first surface and contacts a second side of the filler wire. A portion of the filler wire is located between the first surface and the second surface. A bias device includes a first resilient portion positioned along a shaft. The resilient portion is configured to bias the idler wheel towards the driver wheel. The bias device further includes means for occupying a first distance on the shaft in the biasing direction so as to force the resilient portion to assume a first preset length and occupying a second distance on the shaft in the biasing direction so as to force the resilient portion to assume a second length.
Yet another aspect of the present invention involves a welding filler wire apparatus comprising a frame, a first drive section, a second drive section, a motor, a bias member and an actuator. The first drive section is mounted on the frame and defines a first drive surface for contacting a first side of the filler wire. The second drive is moveably mounted on the frame and defines a second drive surface for contacting a second side of the filler wire. The motor moves at least one of the first drive section and the second drive section. The biasing member is coupled to either of the first drive section or the second drive section. The biasing member exerting a biasing forcing in a biasing direction. The actuator connected to an adjustable spacer. The actuator has a first predetermined position and a second predetermined position. The adjustable spacer is coupled to the actuator and configured such that when the control is in the first position, the adjustable spacer occupies a first amount of space in the biasing direction to force the biasing member to assume a first length so as to exert a first force on at least one of the first drive section and the second drive section. When the actuator is in the second position, the adjustable spacer occupies a second amount of space in the biasing direction to force the biasing member to assume a second length so to exert a second force on at least one of the first drive section and the second drive section.
Still yet another aspect of the present invention involves a welding filler wire apparatus comprising a first frame, a second frame, a first drive section, a second drive section, a motor and a biasing member. The second frame is movable with respect to the first frame. The first drive section defines a first drive surface for contacting a first side of the filler wire. The second drive section defines a second drive surface for contacting a second side of the filler wire. The motor moves at least one of the first drive section and the second drive section. The biasing member acts on one of the first frame and the second frame and mounted on a shaft. An adjustable spacer is also mounted on the shaft. The adjustable spacer has a control to move the adjustable spacer between a first predetermined position and second predetermined position. When the control is in the first position, the biasing member is forced to assume a first length to exert a first force on at least one of the first wheel and the second wheel. When the control is in the second position, the biasing member is forced to assume a second length to exert a second force on at least one of the first wheel and the second wheel.
Another aspect of the present invention involves a welding filler wire feed apparatus for feeding filler wire to a welding gun. The apparatus comprises a main frame, a secondary frame, a first wheel, a second wheel, a motor, and a bias controller. The secondary frame configured to move relative to the main frame. The first wheel defines a first surface for contacting a first side of a filler wire. The first wheel being supported by the main frame. The second wheel defines a second surface for contacting a second side of the filler wire. The second surface generally opposes the first surface. The second wheel is supported by the secondary frame. The motor is connected to at least one of the first wheel and the second wheel so as to selectably drive the at least one of the first wheel and the second wheel. The bias controller includes a first resilient portion that biases the secondary frame such that the second surface is biased towards the first surface. The bias controller having a first preset position and a second preset position. In the first preset position the resilient portion exerts a first force on the secondary frame such that a first engagement force is created between the first surface and the second surface. In the second position, the first surface is distanced from the second surface.
All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiment(s) disclosed.